1. Field of the Invention
The present invention relates to the fabrication of high-power light-emitting devices. More specifically, the present invention relates to a technique for fabricating high-power light-emitting diode arrays based on group III-V nitride semiconductor material by using a wafer bonding method. The method disclosed herein improves the yield rate of high-power light-emitting devices.
2. Related Art
Light-emitting diodes (LEDs), which emit light when electric current is driven through the device, have garnered increasing utility in recent decades as technology has advanced. Early usages of LEDs were largely limited to items such as indicator lights and numeric displays. Today, thanks to technological breakthroughs in semiconductor material development and fabrication process, LEDs are used in a wide variety of consumer and commercial products such as traffic lights, flashlights, large-scale video displays, vehicle lights, exit signs, and so forth.
LEDs can emit light at high levels of intensity in a more energy and cost efficient manner than conventional light bulbs can. LEDs produce more light per watt, have significantly lengthy life spans, and can emit colored light without the need for use of color filters, all of which lower costs and increase efficiency. Their small size and low heat dissipation also expand the range of products in which LEDs can be utilized.
Given the same current density and luminance efficiency, the power of an LED is proportional to the size of its light-emitting area. The larger the light-emitting area, the higher the power of an LED. The size of a typical LED is 300×300 μm2. In order for a single LED to generate high power, its size typically needs to be greater than 1×1 mm2.
Numerous techniques are used in fabricating LEDs. Among others, wafer bonding is a valuable technique for manufacturing high-quality LEDs using InGaAlN semiconductor material. The yield rate of LEDs with a size of 300×300 μm2 fabricated using wafer bonding is typically better than 99.9%. However, when wafer bonding is used to manufacture high-power LEDs with a size greater than 1×1 mm2, the yield rate often drops down to 80%.